The present invention relates to heat exchangers, and especially to small, compact, efficient heat exchangers such as what might be used in cooling lasers.
In the past, it has been common to cool high energy lasers and similar optical or scientific equipment using small efficient heat exchangers which are light in weight and will not interfere with the operation of the laser. One of the most common heat exchangers used in lasers utilizes an aluminum plate fin design, which because of the use of aluminum has a high heat transfer and light weight. Typical heat exchangers utilize liquid and air with the coolant being an ethylene-glycol or similar liquid which is efficient at removing heat from the laser and which is cooled with air passing over cooling fins in the heat exchanger. Because of the high heat transfer of an aluminum heat exchanger design, the heat exchanger experiences a low air pressure drop but can result in potentially severe contamination problems as a result of the ethylene-glycol action on the bare aluminum. Because of the potential contamination, it has been suggested to use stainless steel heat exchangers utilizing plate fins and this design results in a slightly less heat transfer effectiveness than when utilizing aluminum, but substantially increases the weight of the heat exchanger and has potentially severe contamination problems with rust and corrosion at welded and brazed joints. As a result of these problems, Applicant encountered with aluminum and stainless steel plate fin designs, a program was initiated to determine whether a titanium heat exchanger would solve the contamination problems; and at first proved unsuccessful because of the reduced heat transfer through the titanium as compared to the aluminum or stainless steel heat exchangers. A new titanium heat exchanger development program, however, has resulted in a titanium pin fin heat exchanger which utilizes titanium without welded or brazed connections in the liquid side of the heat exchanger, which prevents contamination of the coolant, and which utilizes other metals more efficient at removing heat. The heat exchanger uses thin walls of titanium and is free of contamination of the cooling liquid and is lighter than a stainless steel unit, even though heavier than aluminum. It is accordingly an aim of the present invention to provide a titanium heat exchanger which overcomes inherent limitations of heat transfer through titanium.